In some systems, such as a frequency modulated-continuous wave (FM-CW) ranging radar, typically, a simple sinusoidal signal is produced and processed in some desired way. Under certain circumstances, a complex waveform signal may be produced which signal may be, for example, the combination of two or more simple sinusoidal signals. Such a complex signal may require different processing than does the simple sinusoidal signal or may not be capable of being processed depending on the nature of the processing equipment.
Thus, for example, in the aforementioned radar system having, for example, a triangular modulating waveform wherein one target is present in the radar illumination beam, simple sinusoidal beat frequencies, created by mixing the target illuminating interrogation signal with the signals, reflected from the target, associated respectively with the upswing and downswing portions of the modulating waveforms, are produced from which range and range rate may easily be determined. However, if two or more targets are present in the illumination beam, or if multiple return signals from one target exist, the resultant beat frequency is typically a complex waveform resulting from the combination of the simple sinusoidal beat frequency waveforms associated with each target or from the multiple paths of return from the single target. Further, it has been found that, under some circumstances, the radar will receive a return signal from a first target on one modulation cycle and a return signal from a second target on a subsequent modulation cycle. Therefore, the resulting beat frequencies will be simple sinusoids on each modulation cycle, but the frequency will vary from modulation cycle to modulation cycle. A complex beat frequency or beat frequency that varies from one modulation cycle to another, typically cannot be properly processed by the rather unsophisticated processing equipment typically found in such radar systems. Therefore the presence of such complex waveforms must be detected so that they are not erroneously processed.